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Roughly around 27 MHz is the old "CB" (Citizen's Band, 11 meter) frequency block. The advantage of this band is that it is free to use with limited power. This is the band "walkie talkies" used t...
Answer
#2: Post edited
by
Olin Lathrop
·
2020-08-24T20:07:35Z (over 4 years ago)
- Roughly around 27 MHz is the old "CB" (Citizen's Band, 11 meter) frequency block. The advantage of this band is that it is free to use with limited power. This is the band "walkie talkies" used to use.
I remember back in the 1970s a bunch of us neighborhood kids had such walkie talkies. You could simply buy such things and use them, no license or training required. Of course the units themselves were limited in power for that purpose. More powerful units, like those used by truckers, at least came with some rules of use.- One drawback of the 11 meter band is that the antenna needs to be rather large by today's standards to be reasonably efficient. The walkie talkies we had back in the 1970s had collapsible whip antennas that were probably about a meter long. Even then, that was a serious compromise between good coupling and portability.
The 11 meter band makes sense for toys where a license would be cumbersome and where the transmitter and receiver will be close, a few 10s of meters max. In that case, the antennas don't been to be very efficient, and a few extra mW of battery power for transmitting is irrelevant compared to the battery power needed by the motors anyway.
- Roughly around 27 MHz is the old "CB" (Citizen's Band, 11 meter) frequency block. The advantage of this band is that it is free to use with limited power. This is the band "walkie talkies" used to use.
- I remember back in the 1970s a bunch of us neighborhood kids had walkie talkies. You could simply buy such things and use them, no license or training required. Of course the units themselves were limited in power for that purpose. More powerful units, like those used by truckers, at least came with some rules of use.
- One drawback of the 11 meter band is that the antenna needs to be rather large by today's standards to be reasonably efficient. The walkie talkies we had back in the 1970s had collapsible whip antennas that were probably about a meter long. Even then, that was a serious compromise between good coupling and portability.
- The 11 meter band makes sense for toys where a license would be cumbersome and where the transmitter and receiver will be close, a few 10s of meters max. In that case, the antennas don't been to be very efficient, and a few extra mW of battery power for transmitting is irrelevant compared to the battery power needed by the motors anyway.
- <blockquote>433Mhz is also in CB</blockquote>
- No, it's not. That is one of the ISM (Industrial, Scientific, and Medical) bands in the US. The ISM bands are much more restricted in terms of radiated power, repetition time, and overall duty cycle than CB. The two are very different from each other.
#1: Initial revision
by
Olin Lathrop
·
2020-08-24T12:50:33Z (over 4 years ago)
Roughly around 27 MHz is the old "CB" (Citizen's Band, 11 meter) frequency block. The advantage of this band is that it is free to use with limited power. This is the band "walkie talkies" used to use. I remember back in the 1970s a bunch of us neighborhood kids had such walkie talkies. You could simply buy such things and use them, no license or training required. Of course the units themselves were limited in power for that purpose. More powerful units, like those used by truckers, at least came with some rules of use. One drawback of the 11 meter band is that the antenna needs to be rather large by today's standards to be reasonably efficient. The walkie talkies we had back in the 1970s had collapsible whip antennas that were probably about a meter long. Even then, that was a serious compromise between good coupling and portability. The 11 meter band makes sense for toys where a license would be cumbersome and where the transmitter and receiver will be close, a few 10s of meters max. In that case, the antennas don't been to be very efficient, and a few extra mW of battery power for transmitting is irrelevant compared to the battery power needed by the motors anyway.